Pyridyl alkylguanidines

ABSTRACT

The compounds are novel N-substituted-N&#39;-heterocyclic alkylthioureas, guanidines and 1-nitro-2,2-diaminoethylene compounds which are histamine H 2  -antagonists.

This is a division of application Ser. No. 892,231 filed Mar. 31, 1978, now U.S. Pat. No. 4,166,856 issued Sept. 4, 1979 which is a division of application Ser. No. 686,185 filed May 13, 1976 now U.S. Pat. No. 4,098,898 issued July 4, 1978.

This invention relates to pharmacologically active compounds, to methods for preparing these compounds, to pharmaceutical compositions containing these compounds and to methods of blocking histamine H₂ -receptors by administering these compounds. The compounds of the invention can exist as acid addition salts but, for convenience, reference will be made throughout this specification to the parent compounds.

Many physiologically active substances elicit their biological actions by interaction with specific sites known as receptors. Histamine is such a substance and has a number of biological actions. Those biological actions of histamine which are inhibited by drugs commonly called "antihistamines" of which mepyramine is a typical example, and diphenydramine and chlorpheniramine are other examples are mediated through histamine H₁ -receptors (Ash and Schild, Brit. J. Pharmac. Chemother, 27, 427, (1966)). However, other of the biological actions of histamine are not inhibited by "antihistamines" and actions of this type which are inhibited by a compound described by Black et al. (Nature, 236, 385 (1972)) and called burimamide are mediated through receptors which are defined by Black et al. as histamine H₂ -receptors. Thus histamine h₂ -receptors may be defined as those histamine receptors which are not blocked by mepyramine but are blocked by burimamide. Compounds which block histamine H₂ -receptors are referred to as histamine H₂ -antagonists.

Blockade of histamine H₂ -receptors is of utility in inhibiting the biological actions of histamine which are not inhibited by "antihistamines". Histamine H₂ -antagonists are therefore useful, for example, as inhibitors of gastric acid secretion, as anti-inflammatory agents and as agents which act on the cardiovascular system, for example as inhibitors of the effects of histamine on blood pressure. In the treatment of certain conditions, for example inflammation and in inhibiting the actions of histamine on blood pressure, a combination of histamine H₁ - and H₂ -antagonists is useful. The compounds of this invention are histamine H₂ -antagonists. These compounds are represented by the following formula: ##STR1## wherein X is sulphur, CHNO₂, N.CN or NH; Y is amino, lower alkylamino, di(lower alkyl)amino, lower alkoxy, phenylethyl, imidazolylethyl, allyl, 2,2,2-trifluoroethyl or (CH₂)_(n) R: Z is sulphur or methylene: Het is an imidazole, pyridine, thiazole, isothiazole, oxazole, isoxazole, triazole or thiadiazole ring which ring is optionally substituted by lower alkyl, hydroxy, halogen or amino: n is an integer of from 1 to 12: and R is hydroxy, lower alkoxy, amino or lower alkylamino: provided that when X is NH, Y is 2,2,2-trifluoroethyl or (CH₂)_(n) R and that when X is N.CN, Y is not amino or lower alkylamino, or a pharmaceutically acceptable acid addition salt thereof. It will be understood that the structure illustrated in Formula I is only one of several possible representations and that other tautomeric forms are also covered by the present invention. Throughout the present specification by the terms "lower alkyl" and "lower alkoxy", we mean alkyl and alkoxy groups containing from 1 to 4 carbon atoms.

In one preferred group of compounds X is sulphur, CHNO₂ or N.CN. Y is preferably amino, allyl, 2,2,2-trifluoroethyl, (CH₂)_(n) OH or (CH₂)_(n) NH₂. Z is preferably sulphur and particularly useful compounds are those wherein Het is imidazole, pyridine, thiazole or isothiazole optionally substituted by methyl, hydroxyl, chloro or bromo, for example 4-methyl-4-imidazolyl and 2-thiazolyl.

Specific compounds falling within the scope of the present invention include:

N-cyano-N'-methoxy-N"-[2-(4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

1-nitro-2-hydrazino-2-[2-((4-methyl-5-imidazolyl)methylthio)ethylamino]ethylene,

1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-((4-methyl-5-imidazolyl)methylthio)ethylamino]ethylene,

1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-(2-thiazolyl)methylthio)ethylamino]ethylene,

N-cyano-N'-(2-hydroxyethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-(2-aminoethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-(2-phenylethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-[2-(4-imidazolyl)ethyl]-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-[2-(4-imidazolyl)ethyl]-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]thiourea,

N-cyano-N'-(2-methoxyethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-(7-aminoheptyl)-N"-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-(8-aminooctyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-(4-hydroxybutyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-(2-aminoethyl)-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine,

N-cyano-N'-allyl-N"[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine and

N-cyano-N'-(2-methylaminoethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine.

The compounds of Formula I may be prepared from amines of the following Formula II: ##STR2## wherein Het, Z, m and n have the same significance as in Formula I.

For the production of those compounds of Formula I, wherein X is CHNO₂, N.CN or NH, the amine of Formula II is reacted with a compound of Formula III: ##STR3## wherein X¹ is CHNO₂, N.CN or N.COC₆ H₅, Y has the same significance as in Formula I and A is lower alkyl. The compound of Formula III is in turn produced from the reaction of a compound of Formula IV: ##STR4## wherein X¹ and A have the same significance as in Formula III with an amine of formula YNH₂. Alternatively, when X¹ is CHNO₂, a compound of Formula IVa may be used: ##STR5##

In certain cases it may be convenient first to react the compound of Formula IV with the amine of Formula II to give a compound of Formula V: ##STR6## wherein Het, Z, X¹ and A have the above signifance and then to react the compound of Formula V with the amine of formula YNH₂. This is particularly preferred when Y is amino, aminoalkyl or hydroxyalkyl.

For the production of those compounds wherein X is NH the compound prepared by the above method wherein X¹ is N.CO C₆ H₅ or N.CN is subjected to hydrolysis.

Those compounds of Formula I wherein X is sulphur, may be prepared by the reaction of dithiocarbamic ester of Formula VI: ##STR7## wherein Het and Z, have the same significance as in Formula I and A is lower alkyl.

All the above processes may thus be summarised by the following reaction ##STR8## wherein either B is HetCH₂ Z(CH₂)₂ and D is Y or B is Y and D is HetCH₂ Z(CH₂)₂ the product of the reaction wherein X¹ is N.COC₆ H₅ being submitted to acid hydrolysis to yield the compound wherein X is NH.

Alternatively the compounds of Formula I wherein X is sulphur may be prepared by the reaction of an isothiocyanate of Formula VII: ##STR9## with an amine of formula YNH₂ wherein Y has the same significance as in Formula I.

Alternatively, the amine of Formula II may be reacted with an isothiocyanate of formula Y--N═C═S.

The compounds of Formula I block histamine H₂ -receptors, that is they inhibit the biological actions of histamine which are not inhibited by "antihistamines" such as mepyramine but are inhibited by burmamide. For example, the compounds of this invention have been found to inhibit histamine-stimulated secretion of gastric acid from the lumen-perfused stomachs of rats anaesthetized with urethane, at doses of from 0.5 to 256 micromoles per kilogram intravenously. This procedure is referred to in the above mentioned paper of Ash and Schild. The activity of these compounds as histamine H₂ -antagonists is also demonstrated by their ability to inhibit other actions of histamine which, according to the above mentioned paper of Ash and Schild, are not mediated by histamine H₁ -receptors. For example, they inhibit the actions of histamine on the isolated guinea pig atrium and isolated rat uterus.

The compounds of this invention inhibit the basal secretion of gastric acid and also that stimulated by pentagastrin or by food.

In addition, the compounds of this invention show anti-inflammatory activity. In conventional tests such as the rat paw oedema test, where the oedema is induced by an irritant, the rat paw volume is reduced by suncutaneous injection of doses of a compound of Formula I. In a conventional test, such as the measurement of blood pressure in the anaesthetized rat, the action of the compounds of this invention in inhibiting the vasodilator action of histamine can also be demonstrated. The level of activity of the compounds of this invention is illustrated by the effective dose producing 50% inhibition of gastric acid secretion in the anaesthetized rat and the dose producing 50% inhibition of histamine-induced tachycardia in the isolated guinea pig atrium.

For therapeutic use, the pharmacologically active compounds of the present invention will normally be administered as a pharmaceutical composition comprising as the or an essential active ingredient at least one such compound in the basic form or in the form of an addition salt with a pharmaceutically acceptable acid and in association with a pharmaceutical carrier therefor. Such addition salts include those with hydrochloric, hydrobromic, hydriodic, sulphuric and maleic acids and may conveniently be formed from the corresponding basos of Formula I by standard procedures, for example by treating the base with an acid in a lower alkanol or by the use of ion exchange resins to form the required salt either directly from the base or from a different addition salt.

Pharmaceutical compositions comprising a pharmaceutical carrier and a compound of Formula I or a pharmaceutically acceptable acid addition salt thereof and methods of blocking histamine H₂ -receptors which comprise administering a compound of Formula I or a pharmaceutically acceptable acid addition salt thereof are also objects of this invention. The pharmaceutical carrier employed may be, for example, either a solid or liquid. Exemplary of solid carriers are lactose, torra alba, sucrose, talc, gelatin, agar, pectin, acacia, magnesium stearate, stearic acid and the like. Exemplary of liquid carriers are syrup, peanut oil, olive oil, water and the like.

A wide variety of pharmaceutical forms can be employed. Thus, if a solid carrier is used, the preparation can be tableted, placed in a hard gelatin capsule in powder or pellet form, or in the form of a troche or lozenge. The amount of solid carrier will vary widely but preferably will be from about 25 mg to about 1 g. If a liquid carrier is used, the preparation may be in the form of a syrup, emulsion, soft gelatin capsule, sterile injectable liquid contained for example in an ampoule, or an aqueous or nonaqueous liquid suspension.

The pharmaceutical compositions are prepared by conventional techniques involving procedures such as mixing, granulating and compressing or dissolving the ingredients as appropriate to the desired preparation.

The active ingredient will be present in the compositions in an effective amount to block histamine H₂ -receptors. The route of administration may be oral or parenteral.

Preferably, each dosage unit will contain the active ingredient in an amount of from about 50 mg to about 250 mg.

The active ingredient will preferably be administered one to six times per day. The daily dosage regimen will preferably be from about 150 mg to about 1500 mg.

Advantageously the composition will be made up in a dosage form appropriate to the desired mode of administration, for example as a tablet, capsule, injectable solution or as a cream or ointment for topical application.

The invention is illustrated but in no way limited by the following examples.

EXAMPLE 1 N-Cyano-N'-methoxy-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

A solution of methoxamine (7.0 g), prepared from the hydrochloride and potassium hydroxide in methanol (50 ml) and water (10 ml) was added to a solution of dimethylcyanodithioimidocarbonate (7.3 g) in methanol (40 ml) and stirred at room temperature for 60 hours. A solution of 4-methyl-5-[(2-aminoethyl)thiomethyl]imidazole (8.6 g) in methanol (30 ml) was added and the resulting solution was heated under reflux for 18 hours. Concentration followed by chromatographic purification on a column of silica gel with chloroform-methanol (10:1) as eluant and final recrystallisation from acetonitrile afforded the title compounds m.p. 155°-6°.

(Found: C, 45.0; H, 5.9; N, 31.3; S, 11.9% C₁₀ H₁₆ N₆ OS; requires: C, 44.8; H, 6.0; N, 31.3; S, 11.9%).

EXAMPLE 2 N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]N"-(2,2,2-trifluoroethyl)guanidine

A solution of 2,2,2-trifluoroethylamine (9.9 g), prepared from the hydrochloride and potassium hydroxide in methanol (50 ml) and water (10 ml) was added to a solution of dimethylcyanodithioimidocarbonate (7.3 g) in methanol (40 ml) and stirred at room temperature for 90 hours. Concentration gave a colourless solid that was washed with chloroform and then dissolved in methanol (40 ml). A solution of 4-methyl-5[(2-aminoethyl)thiomethyl]imidazole (3.8 g) in methanol was added and the resulting solution was heated under reflux for 20 hours. Concentration followed by chromatographic purification on a column of silica gel with chloroform-methanol (15:1) as eluant and final recrystallisation from acetonitrile gave the title compound (0.85 g), m.p. 155°-6°. (Found: C, 41.3; H, 4.7; N, 26.3; S, 10.1% C₁₁ H₁₅ F₃ N₆ S; requires: C, 41.2; H, 4.7; N, 26.2; S, 10.0%).

EXAMPLE 3 1-Nitro-2-hydrazino- 2-[2-((4-methyl-5-imidazolyl)methylthio)ethylamino]ethylene

Hydrazine hydrate (1.5 g) was added to a solution of 1-nitro-2-methylthio-2-[2-(4-methyl-5-imidazolyl)methylthio)ethylamino]ethylene (4.7 g) in warm ethanol (200 ml) and the solution was set aside overnight at room temperature. Concentration, followed by recrystallisation of the product from acetonitrile afforded the title compound (2.9 g), m.p. 141.5°-142.5°.

(Found: C, 39.6; H, 6.0; N, 31.0 S, 11.7% C₉ H₁₆ N₆ O₂ S; requires: C, 39.7; H, 5.9; N, 30.9; S, 11.8%).

EXAMPLE 4 1-Nitro-2-[2-((4-methyl-5-imidazolyl)methylthio)ethylamino]2-(2,2,2-trifluoroethylamino)ethylene

A solution of 2,2,2-trifluoroethylamine (4.0 g) from the hydrochloride and potassium hydroxide in methanol (45 ml) and water (5 ml) was added slowly to a suspension of 1-nitro-2-methylsulphinyl-2-methylthio ethylene (3.6 g) in methanol (150 ml) at 0°. The mixture was stirred at room temperature for 24 hours, concentrated and dissolved in chloroform. Filtration, redissolution in a small volume of chloroform and precipitation with hexane afforded an orange crystalline solid. This was dissolved in methanol (25 ml) and a solution of 4-methyl-5-[(2-aminoethyl)thiomethyl]imidazole (2.1 g) in methanol (25 ml) was added. The resulting solution was heated under reflux for 2 hours and set aside at room temperature for 18 hours. Concentration followed by chromatographic purification on a column of silica gel with chloroform-methanol (15.1) as eluant and final crystallisation from ethanol afforded the title compound as a hemi-ethanolate (2.4 g) m.p. 161° (dec).

(Found: C, 39.8; H, 5.2; N, 19.3; S, 9.2%; C₁₁ H₁₆ F₃ N₅ O₂ S.0.5C₂ H₅ OH; requires: C, 39.8; H, 5.3; N, 19.3; S, 8.9%).

EXAMPLE 5 N-Cyano-N'-(2-hydroxyethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

A solution of N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea (2.7 g) (British Specification No. 1397436) and ethanolamine (1.34 g) in ethanol (50 ml) was heated under reflux for 19 hours. Concentration followed by chromatographic purification on a column of silica gel with chlofrom-methanol (10:1) as eluant and final recrystallisation from isopropyl alcohol-acetonitrile gave the title compound, mp. 146°-7°.

(Found: C, 46.8; H, 6.5; N, 29.6; S, 11.2% C₁₁ H₁₈ N₆ OS; requires: C, 46.8; H, 6.4; N, 29.8; S, 11.4%)

EXAMPLE 6 N-Cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-N" (2-phenylethyl)guanidine

A solution of N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea (2.69 g) and 2-phenylethylamine (7.2 g) in acetonitrile (50 ml) was heated under reflux for 24 hours. Following concentration and ether extraction to remove excess 2-phenylethylamine the crude product was chromatographed on a column of silica gel and eluted with ethyl acetate-isopropyl alcohol (4:1). Recrystallisation from ethanol-ether afforded the title compound (1.4 g) m.p. 135°-136°.

(Found: C, 59.8; H, 6.8; N, 24.8; S, 9.4% C₁₇ H₂₂ N₆ S; requires: C, 59.6; H, 6.5; N, 24.5; S, 9.4%).

EXAMPLE 7 N-Cyano-N'-[2-(4-imidazolyl)ethyl]-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

A mixture of N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea (8.07 g) and histamine base (3.36 g) was heated for 3 hours at 100° and then for 3 hours at 130°-140°. The product was chromatographed on a column of silica gel with ethyl acetate/isopropyl alcohol (5:1) as eluent and crystallised by slow evaporation from isopropyl alcohol. Recrystallisation from water afforded the title compound, m.p. 170°-171°.

(Found: C, 50.3; H, 6.2; N, 33.5; S, 9.7% C₁₄ H₂₀ N₈ S; requires: C, 50.6; H, 6.1; N, 33.3; S, 9.7%).

EXAMPLE 8 1-Nitro-2-(2,2,2-trifluoroethylamino)-2-[2-(2-thiazolylmethylthio)ethylamino]ethylene

When, in the procedure of Example 4, 2-[(2-aminoethyl)thiomethyl]thiazole is reacted with the product obtained from the reaction of 2,2,2-trifluoroethylamine and 1-nitro-2-methylsulphinyl-2-methylthioethylene the title compound, m.p. 119°-120° (from ethyl acetate) is produced.

(Found: C, 35.4; H, 3.8; N, 16.3; S, 18.7% C₁₀ H₁₃ F₃ N₄ O₂ S₂ ; requires: C, 35.1; H, 3.8; N, 16.4; S, 18.7%)

EXAMPLE 9 N-[2-(4-imidazolyl)ethyl]-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]thiourea

Sodium ethoxide solution (prepared from 0.46 g sodium in ethanol) was added to a solution of S-methyl-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]dithiocarbonate hydriodide (7.8 g) in ethanol.

Histamine base (2.2 g) was added and the solution was heated under reflux for 48 hours. Concentration followed by chromatographic purification of the product on a column of silica gel with ethyl acetate followed by isopropyl alcohol as eluent afforded the title compound as a glass containing water and isopropyl alcohol.

(Found: C, 46.3; H, 6.3; N, 23.6% (C₁₃ H₂₀ N₆ S₂ +4% C₃ H₇ OH+4.5% H₂ O requires: C, 46.6; H, 6.5; N, 23.7%).

EXAMPLE 10 N-cyano-N'-(2-aminoethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

Reaction of N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea with excess ethylenediamine at room temperature afforded the title compound m.p. 164°-167° (from acetonitrile-ethanol).

(Found: C, 46.9; H, 6.5; N, 35.1; S, 11.1% C₁₁ H₁₉ N₇ S; requires: C, 47.0; H, 6.8; N, 34.8; S, 11.4%).

EXAMPLE 11 N-Cyano-N'-(2-methoxyethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

N-Cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea (4.05 g) was dissolved in 2-methoxyethylamine (15 ml) and heated under reflux for 6 hours. Evaporation of the solvent and chromatographic purification of the residue on a column of silica gel with elution by chloroform and then with chloroform/methanol (20:1) yielded the title compound as a pale yellow oil (2.7 g).

(Found: C, 47.8; H, 7.0; N, 28.0; S, 11.2% C₁₂ H₂₀ N₆ OS; requires: C, 48.6; H, 6.8; N, 28.4; S, 10.8%).

n.m.r. analysis in DMSO-d₆ at 100 mHz:

    ______________________________________                                                     Chemical          Integral                                         Assignment    Shift    Multiplicity                                                                              Found Calc.                                  ______________________________________                                          ##STR10##    2.13     singlet    3.0   3                                      SCH.sub.2 CH.sub.2                                                                           2.59     triplet    2.6   2                                       ##STR11##    3.28 3.4 singletmultiplet                                                                           9.5   9                                      ##STR12##    3.68     singlet    2.0   2                                       ##STR13##    7.17     multiplet  1.6   2                                       ##STR14##    7.47     singlet    0.7   1                                      ______________________________________                                    

EXAMPLE 12 N-Cyano-N'-(7-aminoheptyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

1,7-Diaminoheptane (5.2 g) was warmed gently until molten and to it was added N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea (2.69 g). After stirring for 15 hours at room temperature the reaction mixture was extracted with ether to remove excess of the diamine starting material and these purified on a silica gel chromatographic column, eluting with isopropanol to give the title compound (1.08 g), m.p. 84°-87° C.

(Found: C, 55.0; H, 8.2; N, 27.8; S, 9.0% C₁₆ H₂₉ N₇ S; requires: C, 54.7; H, 8.3; N, 27.9; S, 9.1%).

EXAMPLE 13 N-Cyano-N'-(8-aminooctyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

Using 1.8-diaminooctane as the starting material in the procedure of Example 12 yielded the title compound, m.p. 122°-124° C.

(Found: C, 56.0; H, 8.7; N, 26.6; S, 8.5% C₁₇ H₃₁ N₇ S; requires: C, 55.9; H, 8.5; N, 26.8; S, 8.8%).

EXAMPLE 14 N-Cyano-N'-(10-aminodecyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

Using 1,10-diamodecane as the starting material in the procedure of Example 12 yielded the title compound.

(Found: C, 58.2; H, 9.1; N, 24.8; S, 8.0% C₁₉ H₃₅ N₇ S; requires: C, 58.0; H, 9.0; N, 24.9; S, 8.2%).

n.m.r. analysis in DMSO-d₆ at 100 mHz:

    ______________________________________                                                  Chemical                                                                               Multi-     Integral                                           Assignment  Shift( ) plicity    Found  Calc.                                   ______________________________________                                         (CH.sub.2).sub.6                                                                           1.1-1.6  multiplet  16.0   16                                       ##STR15##  2.13     singlet    3.0    3                                       CH.sub.2 NH.sub.2 + CH.sub.2 S                                                             2.58     multiplet  --     4                                        ##STR16##  3.66     singlet    1.8    2                                       NH.sub.2    4.6      multiplet  --     2                                        ##STR17##  7.41     singlet    1.3    1                                       ______________________________________                                    

EXAMPLE 15

Using 1,3-diaminopropane and 1,4-diaminobutane as the starting material in the procedure of Example 12 yields respectively N-cyano-N'-(3-aminopropyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine and N-cyano-N'-(4-aminobutyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine, m.p. 109°-111° C. (from acetonitrile/ether).

(Found: C, 50.7; H, 7.4; N, 31.8; S, 10.2% C₁₃ H₂₃ N₇ S; required: C, 50.5; H, 7.5; N, 31.7; S, 10.4%).

EXAMPLE 16 N-Cyano-N'-(4-hydroxybutyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

4-Aminobutanol (2.7 g) and N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea (4.05 g) were refluxed in ethanol (30 ml) for 4 hours. The reaction mixture was evaporated to yield an oil which was chromatographed on a silica gel column and eluted with chloroform and chloroform/methanol (20:1) to give the title compound as a colourless oil (1.8 g).

(Found: C, 50.4; H, 7.4; N, 26.8; S, 10.1% C₁₃ H₂₂ N₆ OS; requires: C, 50.3; H, 7.2; N, 27.1; S, 10.3%).

n.m.r. analysis in DMSO-d₆ at 100 mHz:

    ______________________________________                                                  Chemical                                                                               multi-     Integral                                           Assignment Shift ( ) plicity    Found  Calc.                                   ______________________________________                                         CH.sub.2 CH.sub.2                                                                         1.45      multiplet  4.1    4                                        ##STR18## 2.11      singlet    3.0(R) 3                                       SCH.sub.2  2.57      multiplet  2.5    2                                        ##STR19## 3.63      singlet    2.0    2                                       NHCNH      7.0       multiplet  2.1    2                                        ##STR20## 7.41      singlet    0.9    1                                       ______________________________________                                    

EXAMPLE 17 N-(2-Aminoethyl)-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine trihydrochloride

N-Cyano-N'-(2-aminoethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine (1.0 g) (see Example 10) for 1 N hydrochloric acid (20 ml) were refluxed together for 6 hours. Evaporation and crystallisation from methanol/isopropanol gave the title compound (0.6 g), m.p. 195°-196° C.

(Found: C, 33.1; H, 6.3; N, 22.8; S, 8.8; Cl, 28.8% C₁₀ H₂₀ N₆ S.3HCl; requires: C, 32.8; H, 6.3; N, 23.0; S, 8.8; Cl, 29.1%).

EXAMPLE 18 N-Allyl-N'-cyano-N"-[2-((4-methyl-5-imidazolyl)methylthio) ethyl]guanidine

Reaction of allylamine and N-cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]-S-methylisothiourea by the procedure of Example 11 afforded the title compound, m.p. 113°-114° C. (from acetonitrile)

(Found: C, 51.6; H, 6.4; N, 30.1; S, 11.5% C₁₂ H₁₈ N₆ S; requires: C, 51.8; H, 6.5; N, 30.2; S, 11.5%).

EXAMPLE 19 N-Cyano-N'-(2-methylaminoethyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

N-Cyano-N'-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]S-methylisothiourea (5.4 g) and (2-aminoethyl)methylamine (25 ml) were mixed together and left for 15 hours at 20° C. Evaporation to dryness and azeotroping with acetonitrile to remove excess diamine gave a solid residue which was recrystallised from isopropanol to give the title compound (4.8 g), m.p. 146°-148° C.

(Found: C, 48.7; H, 7.3; N, 32.9; S, 10.9% C₁₂ H₂₁ N₇ S; requires: C, 48.8; H, 7.2; N, 33.2; S, 10.9%).

EXAMPLE 20 N-Cyano-N'-(12-aminododecyl)-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine

Using 1,12-diaminododecane as the starting material in the procedure of Example 12 yields the title compound.

EXAMPLE 21

A solution of 4-(4-aminobutyl)imidazole (from the dihydrobromine 3.6 g) and 1-nitro-2,2-bis-methylthioethylene (2.0 g) in acetonitrile (50 ml) is set aside at room temperature for 3 days. The product is chromatographed on a column of silica gel with elution by ethyl acetate to give 1-nitro-2-methylthio-2-[4-(4-imidazolyl)butylamino]ethylene. Reaction of this methylthio compound with hydrazine hydrate in the procedure of Example 3 results in the production of 1-nitro-2-[4-(4-imidazolyl)butylamino]-2-hydrazinoethylene.

EXAMPLE 22 N-Amino-N'-[2-(4-methyl-5-imidazolylmethylthio)ethyl]thiourea

Hydrazine hydrate (0.01 mole) is added to a solution of 2-(4-methyl-5-imidazolylmethylthio)ethyl isothiocyanate (0.01 mole) in ethanol, and stirred for an hour at room temperature to give the title compound.

EXAMPLE 23 N-Dimethylamino-N'-[2-(4-methyl-5-imidazolylmethylthio)ethyl]thiourea

When N,N-dimethylhydrazine is used in place of hydrazine hydrate in the procedure of Example 22, and the mixture allowed to react for two days, the title compound is obtained.

EXAMPLE 24 N-Methylamino-N'-[2-(4-methyl-5-imidazolylmethylthio)ethyl]thiourea

N-tert butoxycarbonyl-N-methylhydrazine (0.01 mole) is added to a solution of 2-(4-methyl-5-imidazolylmethylthio)ethylisothiocyanate (0.01 mole) in ethanol and allowed to react for 24 hours at room temperature to give (N'-t-butoxycarbonyl-1-methyl)-4-[2-(4-methyl-5-imidazolylmethylthio)ethyl]thiosemicarbazide. When the latter is treated with conc. hydrochloric acid and then neutralized, the title compound is obtained.

EXAMPLE 25

Reaction of 4-(4-aminobutyl)imidazole with the following reactants:

N-cyano-N'-methoxy-S-methylisothiourea (see Example 1),

N-cyano-N'-(2,2,2-trifluoroethyl)-S-methylisothiourea (see Example 2) and

1-nitro-2-methylthio-2-(2,2,2-trifluoroethyl)aminoethylene (see Example 4)

results respectively in the following products:

N-cyano-N'-methoxy-N"-[4-(4-imidazolyl)butyl]guanidine,

N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[4-(4-imidazolyl)butyl]guanidine and

1-nitro-2-(2,2,2-trifluoroethylamino)-2-[4-(4-imidazolyl)butylamino]ethylene.

EXAMPLE 26

Reaction of 4-(4-aminobutyl)imidazole with dimethylcyanodithioimidocarbonate gives N-cyano-N'-[4-(4-imidazolyl)butyl]-S-methylisothiourea which when reacted by the procedure of Example 12 with the following compounds:

1,2-diaminoethane,

1,8-diaminooctane,

1,12-diaminododecane and

2-hydroxyethylamine

yields the following products respectively:

N-cyano-N'-(2-aminoethyl)-N"-[4-(4-imidazolyl)butyl]guanidine,

N-cyano-N'-(8-aminooctyl)-N"-[4-(4-imidazolyl)butyl]guanidine,

N-cyano-N'-(12-aminododecyl)-N"-[4-(4-imidazolyl)butyl]guanidine and

N-cyano-N'-(2-hydroxyethyl)-N"-[4-(4-imidazolyl)butyl]guanidine.

EXAMPLE 27

Reaction of 2,2,2-trifluoroethylamine according to the procedure of Example 4 with 1-nitro-2-methylsulphinyl-2-methylthioethylene and then with the following amines:

(a) 3-chloro-2-[(2-aminoethyl)thiomethyl]pyridine,

(b) 3-bromo-2-[(2-aminoethyl)thiomethyl]pyridine,

(c) 3-hydroxy-2-[(2-aminoethyl)thiomethyl]pyridine,

(d) 3-[(2-aminoethyl)thiomethyl]isothiazole,

(e) 4-methyl-5-[(2-aminoethyl)thiomethyl]oxazole,

(f) 3-[(2-aminoethyl)thiomethyl]isoxazole,

(g) 3-[(2-aminoethyl)thiomethyl]-1,2,4-triazole and

(h) 2-[(2-aminoethyl)thiomethyl]-1,3,4-thiadiazole

yields the following products:

(a) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-((3-chloro-2-pyridyl)methylthio)ethylamino]ethylene

(b) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-((3-bromo-2-pyridyl)methylthio)ethylamino]ethylene,

(c) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-((3-hydroxy-2-pyridyl)methylthio)ethylamino]ethylene,

(d) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-(3-isothiazolylmethylthio)ethylamino]ethylene,

(e) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-((4-methyl-5-oxazolyl)methylthio)ethylamino]ethylene,

(f) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-(3-isoxazolylmethylthio)ethylamino]ethylene,

(g) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-((3-(1,2,4-triazolyl)methylthio)ethylamino]ethylene and

(h) 1-nitro-2-(2,2,2-trifluoroethylamino)-2-[2-((2-(1,3,4-thiadiazolyl)methylthio)ethylamino]ethylene

EXAMPLE 28

Using methanolamine in place of ethanolamine in the procedure of Example 5 results in the production of N-cyano-N'-hydroxymethyl-N"-[2-((4-methyl-5-imidazolyl)methylthio)ethyl]guanidine.

EXAMPLE 29

When in the procedure of Example 2 the amines (a) to (h) listed in Example 27 are used in place of 4-methyl-5-[(2-aminoethyl)thiomethyl]imidazole the following compounds are produced respectively:

(a) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-((3-chloro-2-pyridyl)methylthio)ethyl]guanidine,

(b) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-((3-bromo-2-pyridyl)methylthio)ethyl]guanidine,

(c) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-((3-hydroxy-2-pyridyl)methylthio)ethyl]guanidine,

(d) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-(3-isothiazolylmethylthio)ethyl]guanidine,

(e) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-((4-methyl-5-oxazolyl)methylthio)ethyl]guanidine,

(f) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-(3-isoxazolylmethylthio)ethyl]guanidine,

(g) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-((3-(1,2,4-triazolyl)methylthio)ethyl]guanidine and

(h) N-cyano-N'-(2,2,2-trifluoroethyl)-N"-[2-((2-(1,3,4-thiadiazolyl)methylthio)ethyl]guanidine.

Acid hydrolysis of these compounds results respectively in the corresponding disubstituted guanidine i.e., compounds of Formula I wherein X is NH.

EXAMPLE 30

Slow addition of a solution of each of the amines (a) to (h) of Example 27 in dry pyridine under nitrogen to a solution of dicyclohexylcarbodiimide and carbon disulphide in dry pyridine at -10° C. yields the corresponding isothiocyanate (of formula VII above). Reaction of this isothiocyanate with hydrazine hydrate according to the procedure of Example 22 yields respectively:

(a) N-amino-N'-[2-((3-chloro-2-pyridyl)methylthio)ethyl]thiourea,

(b) N-amino-N'-[2-((3-bromo-2-pyridyl)methylthio)ethyl]thiourea,

(c) N-amino-N'-[2-((3-hydroxy-2-pyridyl)methylthio)ethyl]thiourea,

(d) N-amino-N'-[2-(3-isothiazolylmethylthio)ethyl]thiourea,

(e) N-amino-N'-[2-((4-methyl-5-oxazolyl)methylthio)ethyl]thiourea,

(f) N-amino-N'-[2-(3-isoxazolylmethylthio)ethyl]thiourea,

(g) N-amino-N'-[2-((3-(1,2,4-triazolyl)methylthio)ethyl]thiourea and

(h) N-amino-N'-[2-((2-(1,3,4-thiadiazolyl)methylthio)ethyl]thiourea. 

We claim:
 1. A compound of the formula: ##STR21## wherein X is N.CN or NH; Y is di(lower alkyl)amino, lower alkoxy, phenylethyl, allyl, 2,2,2-trifluoroethyl, or (CH₂)_(n) R; Z is sulphur or methylene; Het is a pyridine ring which ring is optionally substituted by lower alkyl, hydroxy, halogen or amino; n is an integer from 1 to 12; and R is hydroxy, lower alkoxy, amino or lower alkylamino; provided that when X is NH, Y is 2,2,2-trifluoroethyl or (CH₂)_(n) R, or a pharmaceutically acceptable acid addition salt thereof.
 2. A compound according to claim 1 wherein x is N.CN.
 3. A compound according to claim 1 wherein Het is pyridine optionally substituted by methyl, hydroxyl, chloro or bromo.
 4. A compound according to claim 1 wherein Y is 2,2,2-trifluoroethyl, (CH₂)_(n) OH or (CH₂)_(n) NH₂.
 5. A compound according to claim 1 wherein Y is lower alkoxy, phenylethyl, 2,2,2-trifluoroethyl or (CH₂)_(n) R; n is an integer from 1 to 11 and R is hydroxy, lower alkoxy or amino.
 6. A compound according to claim 5 wherein n is an integer from 1 to 7 and R is hydroxy or lower alkoxy.
 7. A pharmaceutical composition to block histamine H₂ -receptors comprising in an effective amount to block said receptors a compound according to claim 1 and a pharmaceutical diluent or carrier.
 8. A method of blocking histamine H₂ -receptors which comprises administering to an animal in need thereof in an effective amount to block said receptors a compound of claim
 1. 